1. Technical Field of the Invention
The present invention relates to injection molding and more particularly, to a balanced, multiple-level stack mold having molds, hot runners, a sprue bar, split sprue bars, transition bushings, and melt channels, wherein each mold includes a plurality of first plates having at least one cavity therein and a plurality of second plates having at least one core or core inserts thereon, wherein the first plates simultaneously mate with the second plates, thereby defining a plurality of cavities, and wherein the first plates are all orientated in the same direction and hence the second plates are all orientated in the same direction, thereby producing plastic parts orientated in the same direction.
2. Description of the Related Art
Stack molds are generally known in the prior art and used in conjunction with injection molding machines to produce plastic parts. Most injection molding machines have a clamping mechanism that is hydraulically, mechanically, and/or electrically actuated to open and close the stack mold.
Most stack molds have two or three-levels, wherein each level contains two complementary plates that are brought together when the clamping mechanism of the injection molding machine is moved to the closed position. The complementary plates usually include a plate having at least one cavity therein and a plate having at least one core or core inserts thereon. When these plates mate or are brought together, the cavities and cores cooperate to define at least one cavity in the shape of the plastic parts that are to be molded. Molten plastic is injected into the cavity, and the mold is then moved into the open position to eject the resulting plastic part formed in the cavity.
The obvious benefit of using two-, three-, or four-level stack mold arrangements is an increase in production over a single-level mold arrangement. However, a disadvantage with the two-, three, and four-level stack molds is that the cavity plates and, hence, the core plates or plates having the core inserts thereon, are not all facing in the same direction, thereby requiring complex handling systems for removing and processing the resulting plastic parts. Because the plastic parts are not facing in the same direction upon ejection from the injection molding machine, the handling system that removes and processes the plastic parts needs to perform complex maneuvers. This results in inefficiency and increased cost.
U.S. Pat. No. 5,185,119 to Schad et al. discloses a stack mold for use with an injection molding machine. Each of the mold stations has a cavity plate, and all of the cavity plates are facing in the same direction and, hence, all of the core plates are facing in the same direction. Schad et al. overcame some of the disadvantages in the prior art and simplified the handling system required to process the plastic parts being ejected from the injection molding machine. However, the disadvantage in Schad et al. is that it is a tandem machine which opens, closes, and fills the molds sequentially as opposed to simultaneously. Because Schad et al. uses a sequential process in a tandem machine, output is not maximized.
The present invention is directed to overcoming one or more of the problems and disadvantages set forth above, and providing a balanced, multiple-level stack mold configured such that the cavity plates are facing in the same directions and the cavities in the molds are simultaneously filled with molten plastic, thereby producing plastic parts that are facing in the same direction, which reduces the complexity of the downstream handling system.